Chemiluminescence relates to the production of visible light attributable to a chemical reaction. The important aqueous chemiluminescence substances luminal and lucigenin were discovered in 1928 and 1935, respectively. A series of organic soluble chemiluminescent materials were developed in the early 1960's based upon a study of the luminescent reactions of a number of oxalate compounds. A typical organic system useful for chemiluminescence was disclosed by Bollyky et al., U.S. Pat. No. 3,597,362 and claimed to exhibit a quantum efficiency of about 23% compared with about 3% for the best known available aqueous systems.
In its most basic form the two-component, liquid phase oxalate ester chemical light system must comprise an "oxalate component" comprising an oxalic acid ester and a solvent, and a "peroxide component" comprising hydrogen peroxide and a solvent or mixture of solvents. In addition, an efficient fluorescer must be contained in one of the components. An efficient catalyst, necessary for maximizing intensity and lifetime control, may be contained in one of the components.
The oxalate component provides an oxalate ester-solvent combination which permits suitable ester solubility and storage stability. The peroxide component provides a hydrogen peroxide-solvent combination which permits suitable hydrogen peroxide solubility and storage stability.
The solvents for the two components may be different but should be miscible. At least one solvent solubilizes the efficient fluorescer and at least one solvent solubilizes the efficient catalyst. The fluorescer and at least one solvent solubilizes the efficient catalyst. The fluorescer and catalyst are normally placed as to permit both solubility and storage stability in the final components.
Typical suitable fluorescent compounds for use in the present invention are those which have spectral emission falling between 300 and 1200 nanometers and which are at least partially soluble in the diluent employed. Among these are the conjugated polycyclic aromatic compounds having at least 3 fused rings, such as: anthracene, substituted anthracene, benzanthracene, phenanthrene, substituted anthracene, benzanthracene, phenanthrene, substituted phenanthrene, naphthacene, substituted naphthacene, pentacene, substituted pentacene, perylene, substituted perylene, violanthrone, substituted violanthrone, and the like. Typical substituents for all of these are phenyl, lower alkyl (C.sub.1 -C.sub.6), chloro, bromo, cyano, alkoxy (C.sub.1 -C.sub.16), and other like substituents which do not interfere with the light-generating reaction contemplated herein.
The preferred fluorescers are 9,10-bis(phenylethynyl) anthracene, 1-methoxy-9,10-bis(phenylethynyl)anthracene, perylene, 1,5-dichloro 9,10-bis(phenylethynyl) anthracene, rubrene, monochloro and dichloro substituted 9,10-bis(phenylethynyl) anthracene, 5,12-bis(phenylethynyl) tetracene, 9,10-diphenyl anthracene, and 16,17-dihexyloxyviolanthrone.
The term "peroxide component," as used herein, means a solution of a hydrogen peroxide compound, a hydroperoxide compound, or a peroxide compound in a suitable diluent.
The term "hydrogen peroxide compound" includes (1) hydrogen peroxide and (2) hydrogen peroxide-producing compounds.
Hydrogen peroxide is the preferred hydroperoxide and may be employed as a solution of hydrogen peroxide in a solvent or as an anhydrous hydrogen peroxide compound such as sodium perborate, sodium peroxide, and the like. Whenever hydrogen peroxide is contemplated to be employed, any suitable compound may be substituted which will produce hydrogen peroxide. The hydrogen peroxide concentration in the peroxide component may range from about 0.2M to about 15M. Preferably, the concentration ranges from about 1M to about 2M.
The lifetime and intensity of the chemiluminescent light emitted can be regulated by the use of certain regulators such as:
(1) by the addition of a catalyst which changes the rate of reaction of hydroperoxide. Catalysts which accomplish that objective include those described in M. L. Bender, "Chem. Revs.," Vol. 60, p. 53 (1960). Also, catalysts which alter the rate of reaction or the rate of chemiluminescence include those accelerators of U.S. Pat. No. 3,775,366, and decelerators of U.S. Pat. Nos. 3,691,085 and 3,704,231, or
(2) by the variation of hydroperoxide. Both the type and the concentration of hydroperoxide are critical for the purposes of regulation.
Of the catalysts tried, sodium salicylate and various tetraalkylammonium salicylates have been the most widely used. Lithium carboxylic acid salts, especially lithium salicylate, lithium 5-t-butyl salicylate and lithium 2-chlorobenzoate are excellent catalysts for low temperature hydrogen peroxide/oxalate ester/fluorescer chemiluminescent systems.
As outlined above, chemical light is produced by mixing an oxalate ester and hydrogen peroxide together in the presence of a catalyst and a fluorescer. Typically, fluorescers were chosen that were peroxide stable to provide a long lasting glow. In most instances, a single fluorescer has been used to produce a particularly colored light. In some cases, two or more fluorescers of essentially equivalent stability in peroxide have been mixed to produce a blended color. As an example, a blue emitting fluorescer will be mixed with a red emitting fluorescer to make a pink light.
Of the numerous fluorescers outlined above, relatively few emit light in peroxyoxalate chemiluminescence and are sufficiently peroxide stable (five phenylethynyl anthracenes, one violanthrone, and three perylene dicarboximides) to yield commercially viable products. While other fluorescers are known to emit light they are not peroxide stable, and have historically been rejected for commercial use.
Thus, while chemical lighting devices utilizing such systems have been available commercially for more than two decades, the majority of these devices have emitted a single color. Exceptions have been two, three, or five color devices, e.g. in the form of necklaces, where the multiple colors are discrete bands or sections, each formulated to emit a single color within the device.
In every device, however, the color emitted by the device or section of the device has been a constant, single color. Green starts and stays green, blue starts and stays blue, etc.
Therefore, the instant invention has perfected a process for producing chemical lighting devices which are capable of expressing differently colored lights during the course of the ongoing reaction.